Surface Plasmon Resonance (SPR) offers a detection platform that is versatile, robust, and amenable to complex, multiplexed measurements of samples. The relative speed with which SPR sensorgrams can be generated and analyzed also makes this technique suitable for medium- to high-throughput analysis of multiple samples. Described herein is the use of an SPR assay to define phenotypes of allo- and autoimmune antibody responses based on antigen-specific immunoglobulin subclass distribution and epitope specificity.